1. Field of the Invention
This invention relates to a surgical trephine adapted for boring an opening in tamped bone chips.
2. Description of the Prior Art
Modern surgical techniques, especially as applied to hip prostheses, sometimes require a prosthetic device with an elongated stem. These devices are used when not only are there problems with the hip joint but where there is also the possibility of fracturing in the length of the femur. The addition of a standard length prosthesis stem into such a femur can sometimes create further problems and for this reason a stem of much longer length is employed. The distal portion of such stems is usually parallel because of the extended length and the narrowing of the femur and its intramedullary canal.
In modern techniques bone chips can be employed to line the intramedullary canal and these chips are first tamped into position, for example as described and shown in the Applicants U.S. Pat. No. 5,788,704. This patent shows a method and apparatus for implanting a prosthesis in which a bone cavity is filled with bone chips which are compressed.
When such a technique is used for long prosthesis stems there are difficulties in shaping the distal end of the cavity due, not only to the long length, but also to the possibilities of causing further compression of the bone chips and thus tending to expand the filling and create fractures in the bone structure.
The present invention is intended to provide an instrument which can be used for cutting the required cavity into the bone chips in operations of the kind described above, although it can be used for any cavity in which bone chips are used and a substantially parallel cavity is required.